Thorsten A. Kern

Engineering Haptic Devices

This chapter introduces the philosophical and social aspects of the human haptic sense as a basis for systems addressing this human sensory channel. Several definitions of haptics as a perception and interaction modality are reviewed to serve as a common basis in the course of the book. Typical application areas such as telepresence, training, and interaction with virtual environments and communications are presented, and typical haptic systems from these are reviewed. The use of haptics in technical systems is the topic of this book. But what is haptics in the first place? A common and general definition is given as Definition Haptics Haptics describes the sense of touch and movement and the (mechanical) interactions involving these. but this will probably not suffice for the purpose of this book. This chapter gives a detailed insight into the definition of haptics (Sect. 1.2) and introduces four general classes of applications for haptic systems (Sect. 1.3) as the motivation for the design of haptic systems and—ultimately—for this book. Before that, we give a short summary of the philosophical and social aspects of this human sense (Sect. 1.1). These topics are not addressed any further in this book, but should be kept in mind by every engineer working on haptics. C. Hatzfeld (B) Institute of Electromechanical Design, Technische Universität Darmstadt, Merckstr. 25, 64283 Darmstadt, Germany e-mail: c.hatzfeld@hapticdevices.eu T.A. Kern Continental Automotive GmbH, VDO-Straße 1, 64832 Babenhausen, Germany e-mail: t.kern@hapticdevices.eu

Intravascular palpation and haptic feedback during angioplasty

Within the HapCath - haptic catheter - project an assistive system for interventional catheterizations has been developed. Conventional navigation during catheterization is done by direct manipulation of a handle at a guide wires proximal end. With the aid of x-ray imaging the corresponding movement of the distal tip within the patient can be monitored. Depending on the practical experience of the medical expert and on the varying complexity of the treatment, the procedure differs in duration and x-ray exposure dose of up to 300 %. The aim of the HapCath-System is to reduce duration and exposure dose by simplifying the procedure. The implemented method is to measure the contact forces at the distal tip of the guide wire and feed these measured forces back onto the proximal end of the guide wire to enable tactile feedback and allow for haptic control of the guide wire. The system gives exact measures for the contact force of the guide wires tip and vessel walls to the physician. The demonstration system of HapCath includes an artificial artery system, within these the user will be able to maneuver the haptic guide wire and will be able to recognize different types of plaques by touching the calcifications with the guide wire tip. The system is set up to experience different levels of haptic assistance. The discrete tasks of catheterizations can be performed with visual or haptic feedback either, or with visual and haptic feedback simultaneously.

ISO's Work on Guidance for Haptic and Tactile Interactions

Tactile and haptic interaction is becoming increasingly important and is no longer restricted to assistive technologies and special purpose computing environments. The technology has gone through numerous breakthroughs and replications and is now entering a period of developing empiricism, the phase in which the first benefits of this new development are becoming available. While considerable research exists, the current lack of ergonomic standards results in systems without sufficient concerns for either ergonomics or interoperability, leading to difficulties for users of multiple, incompatible or conflicting applications. ISO (through working group TC159/SC4/WG9) is working toward international standards, which are being dual-tracked as both ISO and CEN standards. This paper gives an update on the status of the Draft International Standard on tactile/haptic interactions and the recently initiated work on a framework for tactile/haptic interactions.

Studies of the Mechanical Impedance of the Index Finger in Multiple Dimensions

For both, the analysis of haptic interaction and the quantification of haptic perception a profound knowledge of the mechanical impedance of human touch are needed. Several models for a users impedance have been suggested in literature and some guidelines and quantitative values from independent models for different contact situations are available. However for the analysis of haptic interaction and the quantification of perception it is necessary to allow comparison between different grasps. Therefore a reduced set of models which covers many types of touch in an acceptable quality would be ideal. Additionally the influence of the change of touch --- the pretension of fingers --- on the impedance is seldom referred to and even more seldom quantified. In 2005 the authors defined a method to quantify the impedance of a three finger precision grasp. In continuation of this approach and with the aim to collect a catalogue of impedance measures, this document presents results from set of 192 measurements regarding the impedance of the index finger from eight subjects. The resulting models and their dependencies are given as approximated plots of the impedance in dependency of frequency, direction of touch and size of the contact area. The resulting curves are discussed and put into context of the influence of impedance.

Design of a haptic display for catheterization

Navigating a catheter inside the patient and orientation during this procedure is mainly dependent on a live x-ray image. Although methods for 3D visualization and remote navigation of the catheter are emerging and subject to tests, still precise positioning is merely the result of intense training and high skills of the performing surgeon. A novel assistance-system intends to provide measured force data from the tip of a guide wire and display them as feedback to the performing surgeon. It is intended to build a simulator giving a first impression of the feel and touch of such an assistance. For this simulator a haptic display is needed. This article refers to design methods and the actual structure of this display. It has to be capable applying torque and force on the catheter. General technical requirements are presented. The realized prototype itself is shown and the experience made is presented.

HapCath: Highly Miniaturized Piezoresistive Force Sensors for Interior Palpation of Vessels during Angioplasty

Medical and industrial telemanipulation and assistive systems require force sensors as a part of the effector interacting with objects or organs. The importance of haptic perception for medical application is still growing and numerous research groups are focusing on utilizing haptic technology in that area. Within the HapCath project, a concept to improve navigation of catheters and guide wires during radiological interventions is put into practice. In this paper a piezoresistive force sensor for measuring contact forces within the arteries is presented. It is manufactured to be mounted at the tip of guide wires with a diameter of 360 μ m. Two different sensor structures are introduced in terms of measurement principles, manufacturing technologies and characterized by measured sensor performance. Technological challenges, e.g. the packaging for medical applications and its effect on sensor performance, are addressed. Future applications for tactile measurements are shown and the advantages, but also the challenges of tactile measurement technology based on piezoresistive force sensors are summarized.

Closed loop stability analysis of an assistance system for catheterization

Catheterizations are standard procedures of todays vascular treatment for diagnosis and therapy. To improve navigation even into smaller branches a novel device with haptic feedback assisting during catheterization is currently being developed. One aspect of the design is the identification of possible sources for instability, which is focused on in this paper. This requires the analysis and modeling of the interaction between the device, the patient and the medical staff. The resulting open loop response plotted in Bode-diagram demonstrates areas of possible instabilities. As a result design constrains to guarantee stability in any possible situation is derived

A remotely controlled lightweight MRI compatible ultrasonic actuator for micrometer positioning of electrodes during neuroethological primate research.

Abstract The precise positioning of microelectrodes is essential for a reliable electrophysiological exploration of anatomical structures in the brain of laboratory animals, e.g., non-human primates in systemic brain research. Despite recent advances in micromechanics, the majority of small, chronically head mounted devices for advancing and retracting electrodes in freely moving animals reported in the literature are manually operated. In this article, we present a newly developed lightweight microfeed, based on an ultrasonic actuator for micrometer positioning of recording microelectrodes. It has been designed for compatibility with magnetic resonance imaging to allow non-invasive visualization of chronically implanted electrodes. The actuator combines a teleoperation via infrared control to minimize manipulation of animals during neuroethological studies. Its design is believed to add substantially to the well-being of experimental animals. Zusammenfassung Die exakte Positionierung von Mikroelektroden ist von hoher Bedeutung für eine zuverlässige elektrophysiologische Erforschung anatomischer Strukturen im Hirn von Labortieren, wie z.B. nicht-humanen Primaten, in der systemischen Hirnforschung. Trotz neuerer Fortschritte in der Mikromechanik dominieren bei den eingesetzten kleinen, dauerhaft am Kopf montierten Geräten zum Vorschub bzw. Rückzug von Elektroden in frei beweglichen Tieren manuelle Vortriebe. In diesem Beitrag beschreiben wir einen neu entwickelten leichten Miniaturvorschub, basierend auf einem Ultraschallaktor zur mikrometergenauen Positionierung von Mikroelektroden. Der Aktor wurde für den Einsatz im Magnetresonanztomographen entworfen und soll die nicht-invasive Darstellung von chronisch implantierten Elektroden im Hirn ermöglichen. Die Steuerung des Vorschubs erfolgt über eine Infrarot-Schnittstelle, die den Einfluss auf die Tiere und deren Manipulation während der neuroethologischen Studien minimiert. Wir sind davon überzeugt, dass der vorgestellte Entwurf die Haltung von Labortieren verbessert.

Improving the prediction of haptic impression user ratings using perception-based weighting methods: experimental evaluation

The prediction of haptic impressions of objects is an interesting topic for system designers. Valid prediction schemes would help to evaluate systems in an early stage of development. This paper investigates the approach of weighting mechanical measurements with three perception-inspired weighting procedures to obtain more accurate predictions of user ratings. Experiments are conducted using a set of five light switches as common examples for passive haptic control elements. The results imply that user ratings are mainly based on tactile information in the range of 10 to 1000 Hz, which is not covered completely by current industrial measurement procedures.

Piezoelectric Ultrasonic Actuator for a Haptic Display for Catheterisation

During a catheterisation, the surgeons navigation to the coronary vessels is restricted to a two-dimensional X-ray image. The HapCath system presents a haptic feedback to the surgeon to enable a more intuitive navigation similar to a blind mans cane. In this paper the actuation system for the haptic interface is shown. A piezoelectric ultrasonic actuator is used to generate force and torque on the guide wire. The main working principle of the actuator is described. The advantages compared to dynamic actuating systems are described